1. Field of the Invention
The present invention relates to a mold and a method of molding semiconductor devices. More particularly, the present invention relates to a mold and a method of molding semiconductor devices capable of preventing a package from warping.
2. Description of the Related Art
Due to the rapid development of multi-media systems, equipment for producing digital images and processing digital images is in great demand. Many types of digital imaging products, for example, PC digital video cameras, digital cameras, optical scanners and imaging phones, are now out in the market. In all these digital products, images are captured through an image sensor. The most common types of image sensors include the charge-coupled device (CCD) and the complementary metal-oxide-semiconductor (CMOS) image sensor. Both types of sensors are sensitive to incident light from an object and can convert the light into a digital signal. Because all these optical devices need to receive the light from the object, the packaging method must differ from most other electronic products.
Conventionally, most optical devices are packaged using ceramic carriers, for example, the ceramic leadless chip carrier (CLCC). Because ceramics has a high thermal dissipation capacity and is resistant to moisture penetration, ceramic packages have high product reliability and are generally used in military or industrial grade products. With the rapid expansion of the electronic industry, more and more optical devices are incorporated into commercial and consumer products. However, if ceramic packages are used in consumer products, cost is a major concern. Since the concern for reliability in commercial or a consumer applications is not so strict, plastic packages are acceptable. In the conventional technique, a common plastic substrate is used in packaging the optical device. Furthermore, to prevent the plastic from affecting the optical characteristics of the package, a transparent packaging material is often used in the packaging process. Yet, the process of injecting the molding material into a mold and waiting the material to cool down often results in a warping of the plastic substrate or the molding compound. In other words, the characteristics of the optical device package may change after the molding process.
Due to market pressure and the need to lower production cost, providing a method capable of lowering the packaging cost of optical sensor while maintaining a moderately high product quality and reliability is an important issue.